A NOVEL TITRATION METHODOLOGY FOR ELUCIDATION OF THE STRUCTURE OF PREFORMED COOKED CURED MEAT PIGMENT BY VISIBLE SPECTROSCOPY

The chemical structure of preformed cooked cured-meat pigment (CCMP), which is believed to be the pigment of thermally-processed nitrite-cur ed meat, was investigated by a novel titration methodology. Electronic spectra of reduced haemin and its nitrosyl derivative were recorded i n the visible region in an aqueous- or a dimethyl sulphoxide-medium. C hanges in the electronic spectrum of reduced haemin upon gradual addit ion of aliquots of a saturated solution of nitric oxide (NO) revealed that only one molecule of NO ligates itself to the iron of the porphyr in molecule. A similar conclusion was reached from the infrared studie s of CCMP, which revealed the presence of only one N-O stretching band . Thus, preformed CCMP is irrefutably a mononitrosyl, not a dinitrosyl , derivative of reduced haemin. This conclusion is further supported b y an independent electron paramagnetic resonance study of CCMP, which showed that the pigment was a pentacoordinated paramagnetic complex. C opyright (C) 1996 Elsevier Science Ltd